Capsule with solar particles to be captured in mid-air
The first space mission to bring back material from beyond the Moon is scheduled to culminate on 8 September with the airborne retrieval of the sample return capsule from NASA's Genesis spacecraft, launched in August 2001 to collect particles from the Sun.
The 190kg (420lb) capsule containing 10-20 micrograms of solar wind particles is intended to be captured in mid-air by a helicopter over the US Air Force's Utah Test & Training Range. Primary and back-up Eurocopter AS350B2s flown by stunt pilots have each been equipped with a 5.6m (18.5ft)-long pole and winch with 137m of Kevlar cable and a hook with which to snag the capsule's 10.5m-wide parafoil as it descends in a slow spiral.
The first capture attempt will be made when the capsule, descending at 12ft/s (3.6m/s), reaches 9,000ft altitude. The helicopter will lower the pole and hook to a 50° angle while approaching from behind, overtaking the capsule at 23-98ft/s with its skids about 2.5m above the parafoil.
The parafoil fabric will wrap round the pole then slide down into the hook, which will reel out on the cable as the helicopter pitches up to slow down and prevent the parafoil re-inflating.
If the first attempt fails, the second helicopter will be in position 300m behind, setting up for its approach. NASA estimates there will be five opportunities for a mid-air retrieval before the capsule descends below 1,500ft for a hard landing. Practice runs were 100% successful, says the agency. The same retrieval procedure is planned for the January 2006 return of samples from the comet Wild 2 by NASA's Stardust spacecraft.
GRAHAM WARWICK / WASHINGTON DC
Source: Flight International
